sanity check: in single user mode, only test for admin user if migrations have been completed

classes/config.php

@@ -484,7 +484,8 @@ class Config {
 			array_push($errors, "Data export cache is not writable (chmod -R 777 ".self::get(Config::CACHE_DIR)."/export)");
 		}
 
-		if (self::get(Config::SINGLE_USER_MODE) && class_exists("PDO")) {
+		// ttrss_users won't be there on initial startup (before migrations are done)
+		if (!Config::is_migration_needed() && self::get(Config::SINGLE_USER_MODE) && class_exists("PDO")) {
 			if (UserHelper::get_login_by_id(1) != "admin") {
 				array_push($errors, "SINGLE_USER_MODE is enabled but default admin account (ID: 1) is not found.");
 			}